1. Field
The present disclosure relates to a circuit breaker, and more particularly to a circuit breaker configured to be installed at a wiring.
2. Background
Generally, a circuit breaker is a power device for detecting an abnormal current to automatically break the circuit, thereby protecting life, an electrical load device, and a circuit from an accident current in a power supply circuit between the power source and the load, when the abnormal current such as an over current, an electric shortage current, or the like is generated in the circuit. The circuit breaker is compulsorily installed on a wiring at a house and a factory, for example.
The circuit breaker may be categorized into two types based on operation method, that is, an electronic circuit breaker that operates using a leakage detecting chip, and a circuit breaker in which a trip coil is directly connected to a secondary winding of a ZCT (Zero-phase Current Transformer), where the latter is largely used.
FIG. 1 is a lateral view illustrating a trip coil assembly of a circuit breaker according to prior art, and FIG. 2 is a perspective view illustrating a trip coil assembly of a circuit breaker according to prior art.
The trip coil assembly according to the conventional circuit breaker includes a permanent magnet (10), a yoke (20) forming a magnetic path of a magnetic field induced by the permanent magnet (10), a bracket (30) mounted on the yoke (20) to fix the yoke (20) to the permanent magnet (10), a lever (40) contacted to one side of the yoke (20) to release a connection with a mechanism of the circuit breaker, a trip coil (50) directly connected to a secondary winding of a ZCT, and a spring (60) mounted on the bracket (30) and connected to the lever (40) to provide elasticity to the lever (40).
Now, operation of the conventional circuit breaker will be described.
A current in proportion to a leakage current flows in the trip coil (50) connected to the secondary winding of the ZCT when a leakage occurs, a magnetic field formed by the permanent magnet (10) is offset by an AC magnetic field generated thereby, and the lever (40) is activated the moment the magnetic field is offset to activate the circuit breaker in response to operation of a device connected to the mechanism.
The circuit breaker thus described is such that the energy of the permanent magnet (10) is very small, because the magnetic field of the permanent magnet (10) is offset by using a current of several milliampere flowing in the secondary winding of the ZCT in case a leakage occurs. Generally, the force by the conventional permanent magnet (i.e., the energy) is obtained by multiplication by coercivity (Hc) and residual magnetic flux density (Br), which is BH characteristic.
In case products are mass-manufactured corresponding to respectively different sensitivity currents, for example, in case the sensitivity currents are 30 mA, 100 mA and 300 mA, an energy intensity of a permanent magnet with a sensitivity current of 300 mA is generally greater than that of a permanent magnet with a sensitivity current of 30 mA.
A demagnetization method is representatively used for setting up an energy intensity of a permanent magnet. The demagnetization method is a method in which an AC current-flowing electronic magnet is made to approach a vicinity of an assembled RCCB (Residual-Current Circuit Breaker) to demagnetize the intensity of the permanent magnet assembled inside the RCCB.
However, the demagnetization method thus described is disadvantageously problematic in that a desired sensitivity current value can be obtained only through several repeated performances of demagnetization, because an accurate demagnetization is not obtainable by a one-time process, and a remagnetization process must be added for over-magnetized products caused by erroneous operation of an operator, thereby complicating the work and lengthening the work time.